Predicted to go extinct by the year 2100, coral reefs are thought to be the quintessential climate change victims.

But new research shows the reefs are actually putting up a better fight against warming waters than previously thought.

Scientists at CSU Monterey Bay discovered coral reefs are adapting to the temperature changes after they realized current reef populations are larger than what predictive models said they should be. That meant coral bleaching, which occurs when warming waters cause reefs to expel the algae that give them their color, was less prevalent than anticipated.

"The model over-predicted present levels of coral bleaching," said lead author Cheryl Logan. "This led us to believe that maybe the future predictions were over-predicting too."

To test their theory, the researchers investigated some of the reefs' known adaptive responses and added those variables into the predictive models. The reef populations could adapt through genetic alterations, which occur over generations, or through acclimation, which occur in one reef's lifetime.

Another adaptive method, symbiont shuffling, occurs when a reef gets rid of the weaker algae that covers it and instead allows only algae that is resistant to warm water. Only some reefs can perform this last method.

When the researchers built these factors into the model, they found that 14 percent more of the surviving reef cells were predicted to resist bleaching in 2100.

The researchers also found that depending on carbon levels, the number of coral reefs present in the year 2100 may be between 20 percent and 80 percent of what is present now. The range is so wide because carbon emission levels, which can exacerbate coral bleaching, can vary greatly in the future, Logan said.

"Early suggestions said that the reefs would be gone by mid-century," she said. "Ours shows that if the corals can adapt to the warming temperatures of the past 40 to 60 years, then some may still persist until the end of the century."

The results appeared in the Oct. 29 edition of the journal Global Change Biology.

"The work illuminates the complexity of predicting future ecosystem trends," said Adina Paytan, a marine scientist from UC Santa Cruz who was not involved in the study, in an email. "We need to try to identify the zones most likely to be less impacted and conserve and protect them."

Logan said she plans to refine the image of coral reef bleaching in hopes of better informing policymakers.

Although the study spells good news for coral reefs, it does have some caveats, Logan said.

The study only looked at the effects of coral adaptation against coral bleaching and not at pollution, coral disease and ocean acidification, which also threaten reef numbers.

The researchers stressed that to keep the reefs from throwing in the towel, humans need to lower global carbon emission levels. If scientists better understand how the reefs are already adapting to climate change, Logan said, people can help boost these adaptations and ensure the reefs survive into the next century.